This project constitutes the continuation of efforts to develop the acellular slime mold, Physarum polycephalum, as a model system for correlated biochemical, genetic, ultrastructural, and phenomenological studies of eukaryotic cell movements. During the next fiscal year several projects will be completed, pending - in some cases - the reestablishment of healty microplasmodial cultures. Amino-acid analyses of plasmodial actin will be completed, peptide maps in comparison with muscle actin will be prepared, and the sequencing of difference peptides will commence. Studies of actin disassembly in plasmodial homogenates will continue. The purification and characterization of plasmodial myosin will be completed and data concerning its interaction with actin will be collected. Detailed analyses of the fine structure (EM) and motile patterns of microplasmodia will continue. Amoebal colony mutants and amoebo-flagellate transformation mutants will be characterized in more detail with particular emphasis on the link(s) between the two phenotypic variations. More data will be collected on the factors which myxamoebae use to organize their movements with respect both to other amoebae and to their bacterial food source. Preliminary efforts to isolate, by direct selection gechniques, amoebal motility mutants will be extended and attempts made to define mutants which also affect the plasmodial stage. Continued analysis of the amoebo-flagellate transformation will emphasize (1) higher resolution light-micrscopic analyses of living and fixed cells, (2) further studies of the dirstibution of microfilaments and microtubules employing improved EM techniques, and (3) efforts to overcome problems of proteolysis and to characterize amoebal actin,tubulin, etc.